Sydkoster, Sweden offers 1 beach perfect for sunbathing, surfing, swimming, and more. Sydkoster is known for Kosterhavet National Park, Sweden's first marine national park. The best time to travel to Sydkoster, Sweden, is during the summer months of June to August, when the average air temperature is around 18°C (64°F) and the water temperature is approximately 17°C (63°F). Sandee provides detailed maps, photos, and reviews from fellow beachgoers to help you Choose Your Beach™ and plan your perfect beach vacation!